INTRODUCTION Identifying and explaining patterns of geograph- ical distribution of species are the major conceptual goals of phylogeography (Bermingham and Moritz, 1998; Avise, 2000; Kelt and Brown, 2000). Phylo- geographical patterns among animals from the Pacific coast of Mexico have been studied by sever- al authors (e.g., western lyresnake Trimorphodon biscutatus — Devitt, 2006; Bursera — Becerra, 2005), mainly focusing on nonvolant vertebrates but only rarely on bats (Hoffmann and Baker, 2001, 2003). Bats are the second largest group of mam- mals at the Pacific coast of Mexico (Ceballos and García, 1995), and so far were not considered in a phylogeographic context in that area. However, for several species of mammals inhabiting the Pacific coast of Mexico, small geographic ranges and high endemism rates are reported (Ceballos et al., 2002). Mexico’s Pacific coast is extremely rich in endemic species (Ceballos et al., 2002), including 11 restrict- ed species of bats (Ceballos and García, 1995), one of which, Musonycteris, belongs to a monotypic genus (Tellez and Ortega, 1999). Wilkinson and Fleming (1996) provided a very restricted descrip- tion of the genetic structure of Leptonycteris cura- soae across its geographical range and showed a dis- tinct divergence between clades from Western Mexico and the foothills of the Western Sierra Madre. Phylogeographical analyses of mammal dis- tributions along the Pacific coast of Mexico may evaluate the influence of mountain ranges and other biogeographical barriers on the animals and explain similar distribution patterns between species. The tropical dry forest is one of the major ecosystems in Mexico, but is also among the most heavily utilized, perturbed, and least conserved of the large tropical ecosystems (Quesada and Stoner, Acta Chiropterologica, 11(2): 259–269, 2009 PL ISSN 1508-1109 © Museum and Institute of Zoology PAS doi: 10.3161/150811009X485503 Phylogeography of Musonycteris harrisoni along the Pacific coast of Mexico JORGE ORTEGA 1, 6 , MARCO TSCHAPKA 2 , TANIA P. GONZÁLEZ-TERRAZAS 3 , GERARDO SUZÁN 4 , and RODRIGO A. MEDELLÍN 5 1 Laboratorio de Ictiología y Limnología, Posgrado en Ciencias Químico-Biológicas, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Prolongación de Carpio y Plan de Ayala s/n, Col. Sto. Tomas, 11340, México City, D.F., México 2 Institute for Experimental Ecology, University of Ulm, Albert-Einstein Allee 11, D-89069 Ulm, Germany 3, 5 Laboratorio de Ecología y Conservación de Vertebrados, Departamento de Ecología de la Biodiversidad, Instituto de Ecología, Universidad Nacional Autónoma de México, Circuito Exterior junto a Jardín Botánico, 04510, México City, D.F., México 4 Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, México City, D.F., México 6 Corresponding author: artibeus2@aol.com The goal of this study was to assess the phylogeography of the trumpet nosed-bat (Musonycteris harrisoni) through an analysis of the phylogeographic relationship among populations over its entire distributional range along the Pacific coast of Mexico. We used nucleotide sequence data from the mitochondrial cytochrome-b (≈ 950 bp) and D-loop to assess levels of intraspecific variation in the species. DNA-samples of M. harrisoni were obtained from museums, own field collections and bats provided by other researchers. We analyzed samples collected from 21 different localities. Molecular sequence data were analyzed using neighbour- joining, maximum likelihood and Bayesian studies. Nested clades analyses were used to assess the cladistic arrangement of haplotypes. Across the 21 distinct localities, we found nine haplotypes using cytochrome-b data, and 11 different haplotypes using the D-loop. Nested clade analysis revealed a moderate level of molecular variance among localities. Localities were grouped into two clades, composed of individuals from either the northern or southern portion of the species’ range that accounted for 41% of the genetic variance. The northern clade shows little phylogenetic structure and distribution seems to be restricted by the Sierra Madre mountain range. Our results suggest a pattern consistent with the vicariant allopatric divergence/speciation model, influenced by habitat loss and fragmentation. Key words: cytochrome-b, D-loop, endemism, Musonycteris harrisoni, Pacific coast of Mexico, phylogeography, tropical dry forest